Disk processing systems are commonly used to manufacture magnetic disks for hard disk drives. These systems generally include several process stations that work together to deposit thin layers of material onto a substrate. Each process station comprises a sealed chamber which is maintained at a partial vacuum as a thin film deposition process is carried out. The chambers are coupled together in way that maintains the partial vacuum as the substrates are moved between the stations.
A load lock may be used to interface the vacuum controlled environment within the disk processing system with the external environment. Specifically, the load lock provides a means by which substrates may be loaded into the disk processing system without disturbing the internal vacuum controlled environment. The load lock comprises a load lock chamber and a pumping system. The loading process begins by sealing the load lock chamber and venting it to atmospheric pressure. One or more substrates are then introduced into the load lock chamber through a door or other passageway. The door is then closed to seal the load lock chamber. Once sealed, the load lock chamber is evacuated by a vacuum pump through a roughing valve until a partial vacuum is reached. The substrates are then removed from the load lock chamber through a gate valve which interfaces the chamber to a process station within the disk processing system. The gate valve is then closed and the load lock chamber is vented to atmospheric pressure before introducing more substrates into the chamber. A load lock may also be positioned at the output to the disk processing system to facilitate the removal of finished articles from the system in a similar manner.
The operation of the vacuum pump during the evacuation process tends to cause a turbulent flow of gas in the load lock chamber. As a result, microscopic particles on the inner surfaces of the chamber may become dislodged. These microscopic particles are carried by the flow and distributed throughout the chamber. Many of these particles come into contact with and adhere to the surface of the substrates within the chamber. These particles interfere with the deposition of material during downstream processes in the disk processing system, which results in defects in the finished article.
Accordingly, there is a need to reduce the particulate contamination of substrates in load locks during the evacuation process in disk processing systems and other machines.